The present invention relates to an electromagnetic fuel injection valve for use in an internal combustion engine.
The conventional typical electromagnetic fuel injection valve has structure and shape shown in FIG. 7.
A solenoid coil 4 is disposed in a housing made of magnetic material. A stationary core 3 made of magnetic material is inserted into the solenoid coil 4. A movable core 2 made of magnetic material is positioned so as to face the stationary core 3. The movable core 2 is urged by a spring 7 and the preset load of the spring 7 is adjusted by the position of an adjusting pipe 8. Further, the movable core 2 is electromagnetically driven by the solenoid coil 4 and integrally connected with a needle valve 5 which is slidally fitted in a valve housing 6 so as to control the injection of a fuel in cooperation with a seat 6a formed within the housing 6.
In the above-described structure, the housing 1 is required to have a complicated shape since it receives therein the valve housing 6, solenoid coil 4 and the like while performing its function as one of elements of a magnetic circuit.
To satisfy such requirement, it has been usual that the housing 1 which is made of a ferromagnetic material such as 12Cr electromagnetic stainless steel is manufactured in such a manner that it is roughly molded to a predetermined shape by cold forging and fitting sections and insert holes of the housing requiring precision are finished by cutting thereby reducing the material and working costs.
However, in the case of cold forging, the shapes to which the housing is molded are limited. Especially, as the housing is required to have a jutted portion 1b facing the movable core 2 which is an important element in forming the magnetic circuit, it has been usual that the molding shape is restricted and as a result, a considerable amount of cutting has to be performed which leads to a large loss of material yield and an increase in the cost required for cutting.